Micro-services have been a hot topic for us folk at Webjet. Like many other software teams, at Webjet, we have been working over the years with what we would more recently call a monolithic architecture.  Being faced with changing the way we engineer our solutions to meet the scale, agility and momentum our business demands, we turned to micro-services as a solution for delivering new features.   This decision led to an unexpected journey with Docker which we would like to share with the broader community

Where did our journey start, what is a monolith ?

In simple terms, a monolithic application (monolith) is an application where the user interface tier and its data access code are stitched together in a single application on a single platform. As the application grows, more service tiers and application features are introduced and therefore the complexity and configuration of the application and its environment increases. It becomes harder to make even the smallest changes and introducing a breaking change can happen at the blink of an eye. Scaling therefore also becomes a resource-expensive effort, as only whole instances of the entire application can be scaled even though each layer has different load and resources requirements. This leads to over-scaling some layers, but under-scaling others.
So how did we break the shackles of the monolith?
Over time, we started slicing up the monolith into separate services and user interfaces that would become isolated. We would deploy each of these services separately using the Microsoft Azure WebApp platform.

Although this was the first step to a micro-service architecture, we introduced a lot of complexities in our build and continuous integration pipelines. As the number of services grew deployments and setting up CI/CD pipelines took a lot of unnecessary time. We were at a point where we could see that the way we were building and deploying our micro-services would soon hit a bottleneck and slow our journey down.

Where the unexpected journey happened.

Being focused on continually improving our engineering processes, we started a review of how we were deploying our WebApps in our CI/CD pipeline.
WebApps allow you to deploy services on separate servers or to the same pool of servers. Deploying a tiny micro-service to its own server does not sound very efficient. Deploying a few of them sounded like a better option, but what if you have one resource hungry noisy neighbour?

This is where Docker comes in.

Docker is a technology that allows us to build all application code, its operating system, configuration and dependencies into one single entity called a container. For us, it made sense to start building new services on container technology and start the decoupling process of the monolithic application. As a group, we’d have to identify all the components of the monolith that we can break apart, -.e.g flight search, hotel search, shopping carts, up-sell services, autocomplete services, small UI components, etc. , etc. 

For the shift to Docker to happen, we needed a massive technology and mindset shift:, introducing new programming languages, new operating system platforms, new scripting frameworks and many more. 

Docker introduced true immutable applications, the ability to run cross platform and on any cloud. Our Docker solution is also highly scalable and deploys really fast! I can go on and on about the beauties of Docker, but I’ll leave this here if you want to read more on what it is. 

With Docker, we can build layers of images. So as an example, let’s say we use Linux Alpine as a base operating system. Our DevOps team can then build a Webjet certified Linux Alpine image with all the required security patches. This can be used to build a other images that have the dependencies for applications to run, for example, a popular programming language built by Google called GoLang 

We embarked on a mission to start building out our base Docker image library to make it really simple for teams to build micro-services on different languages. If I was a developer and I needed to use GoLang as a language, I can simply build a new Docker image for my application and inherit the Webjet GoLang image. An example hierarchy can look like this:

Now, Webjet development teams can build services top down not worrying about the low level configuration, whilst DevOps and security teams can architect the base images from bottom up to ensure they all stem from the certified base images. This keeps vulnerabilities to a minimum and keep the images lean and small as possible. 

We’ve also utilised Azure Container Registry for hosting our Docker images which makes it easy to start integrating continuous delivery pipelines and deploying micro-services. 

This brings us to Part 2 of this series where we’ll be covering “Container Orchestration” and Kubernetes: How we at Webjet deploy and manage a large number of containers within the Microsoft Azure cloud infrastructure. 

Until next time!